Page:NIOSH Manual of Analytical Methods - 1025.pdf/3

 1- and 2-BR OM OP RO PAN E: ME TH OD 1025, Issue 1, dated 1 5 Ma rch 2003 - Page 3 of 4 9. Determ ine desorption efficiency (DE) at least once for each lot of Anas orb CSC or Anasorb CMS used for sam pling in the calibration ranges (step 8). a. Prepare three tubes at each of five levels p lus three m edia blank s. b. Inject a known amount of DE stock solution (5 to 25 :L) directly onto the front sorbent section of each tube with a microliter syringe. c. Allow the tubes to air equilibrate for several minutes, then cap the ends o f eac h tube an d allow to stan d overnight. d. De sorb (ste ps 5 -7) and a nalyze togeth er with stan dard s an d blan ks (step s 11 and 12). e. Prepare a graph of DE vs :g analyte recovered. 10. Analyze a minimum of three quality control blind spikes and three analyst spikes to ensure that the calibra tion gra ph a nd D E graph are in c ontro l.

MEASUREMENT: 11. Set gas chro m atog raph acc ording to m anu facturer’s recom m end ations and to conditions given on page 1025-1. Inject a 1-:L sample aliquot manually using the solvent flush technique or with an autosam pler. NOTE: If peak area is abo ve the linear ra nge of the working standard s, dilute with solvent, reanalyze, and apply the appropriate dilution factor in the calculations. 12. Measure peak areas.

CALCULATIONS: 13. Determine the m ass, :g (corrected for DE), of analyte found in the sam ple front (W f) and back (W b) sorbent sections, and in the average m edia blank front (B f) and back (B b) sorben t sec tions. NO TE : If W b > W f/10, report b reak throu gh a nd p oss ible sam ple loss. 14. Calculate conce ntration, C, of analyte in the air volume sam pled, V(L):

EVALUATION OF METHOD: Desorption efficiency was checked for 1- and 2-bromopropane by spiking known amounts (in CS 2) on 2 different sorbents, Anasorb CSC and Anasorb CMS. The effect of volatility on sample recovery was also determined for each ana lyte spiked on Anaso rb CSC and Anasorb C MS s orbent tu bes using G elA ir po rtable pumps to pull air throug h ea ch tube a t 0.2 L/min for 60 minutes (total volume was 12 L). Storage stability was dete rm ined for ea ch analyte after 7, 1 4, and 30 days. The average DE determined for 1-bromopropane from Anasorb CSC was 96.8% (RSD = 0.015) and for 2bromopropane was 101.0% (RSD = 0.020). W hen air was pulled through spiked sorbent tubes to determine the effects of volatility on sample recovery, the average DE determined for 1-bromopropane was 103.7% (RS D = 0.013) an d for 2-brom opro pan e wa s 99 .7% (RS D = 0.026). The average 30-day storage stability recovery for 1-bromopropane on Anasorb CSC was 106.9% (RSD = 0.009) and for 2-bromopropane was 98.2% (RSD = 0.013). The 30 day storage recovery using Anasorb CMS was 106% (RSD = 0.014) for 1-Bromopropane and 100.6% for 2-Bromopropane.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition